Dynamic Boot Image Streaming

ABSTRACT

The present disclosure describes apparatuses and techniques for dynamic boot image streaming. In some aspects a memory controller that is streaming multiple boot images from a first memory to a second memory is stalled, a descriptor for streaming one of the multiple boot images from the first memory to a non-contiguous memory location is generated while the memory controller is stalled, and the memory controller is resumed effective to cause the memory controller to stream, based on the descriptor generated while the memory controller is stalled, the second boot image to the non-contiguous memory location.

RELATED APPLICATION

This present disclosure claims priority to U.S. Provisional Patent Application Ser. No. 61/560,217 filed Nov. 15, 2011, the disclosure of which is incorporated by reference herein in its entirety.

BACKGROUND

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Computing and electronic devices often include various types of memory for storing data of operating systems, applications, or user files. Before an operating system and applications are run on the device, however, low-level code is used to configure and boot the device. When booting a device, the low-level code is typically copied from one of the memories and executed by a processor in order to configure the components of the device for operation. The memory storing the low-level code is often a non-volatile memory, from which the low-level code is copied into another memory prior to execution. Due to recent advances in memory-controller technology, this low-level code may be streamed to the other memory with minimal initialization or overhead, which may increase a speed at which the device boots.

Memory controllers capable of streaming the low-level code from the non-volatile memory, however, stream the low-level code to contiguous locations of the other memory. This other memory, however, may not have enough capacity to receive all of the low-level code or be a memory from which execution of some of the low-level code is not optimal. Accordingly, some partial solutions prevent streaming until the memory controller is fully initialized. Waiting until the memory controller is fully initialized, however, often consumes considerable time and processing resources, which results in slower device boot times.

SUMMARY

This summary is provided to introduce subject matter that is further described below in the Detailed Description and Drawings. Accordingly, this Summary should not be considered to describe essential features nor used to limit the scope of the claimed subject matter.

A method is described for stalling a memory controller that is streaming, via a direct memory access (DMA) operation, multiple boot images from a first memory to a second memory, generating, while the memory controller is stalled, a descriptor for streaming a second one of the multiple boot images from the first memory to a non-contiguous memory location, and resuming the memory controller effective to cause the memory controller to stream, based on the descriptor and via another DMA operation, the second boot image to the non-contiguous memory location.

A memory storage device is described that includes memory storage media storing multiple boot images executable by a processor of a host device to initialize components of the host device during a boot sequence, a header executable by the processor of the host device to construct a series of data transfer commands for streaming the multiple boot images to non-contiguous locations of another memory storage device, another data transfer command associated with the header executable by a memory controller to stream the header to a base address of the other memory storage device, and a data link command executable by the controller to stall the DMA engine effective to permit the header to be executed from the other memory storage device by the processor to construct the series of data transfer commands for streaming the multiple boot images.

A computing device is described that includes a stream manager that is configured to stall a memory controller while the memory controller is streaming, via a direct memory access (DMA) operation, multiple boot images from a non-volatile memory of the computing device to a volatile memory of the computing device, the memory controller stalled after streaming a first one of the multiple boot images to the volatile memory. Additionally, the stream manager generates, while the memory controller is stalled and based on the first boot image streamed to the volatile memory, a descriptor for streaming a second one of the multiple boot images from the non-volatile memory to a non-contiguous location of the volatile memory. The stream manager then resumes the memory controller effective to cause the memory controller to stream, based on the descriptor and via another DMA operation, the second boot image to the non-contiguous location of the volatile memory.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures, the left-most digit of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different instances in the description and the figures indicate like elements.

FIG. 1 illustrates an operating environment having computing devices in accordance with one or more aspects.

FIG. 2 illustrates an example of embedded flash memory of FIG. 1 in accordance with one or more aspects.

FIG. 3 illustrates a method for stalling a memory controller that is streaming multiple boot images.

FIG. 4 illustrates an example allocation of boot images in accordance with one or more aspects.

FIG. 5 illustrates a method for streaming boot images to non-contiguous locations of a memory device.

FIG. 6 illustrates a method for streaming boot images to multiple memory devices.

FIG. 7 illustrates a System-on-Chip (SoC) environment for implementing aspects of the techniques described herein.

DETAILED DESCRIPTION

Conventional techniques for streaming boot images stream boot images from one memory to contiguous locations of another memory. For example, an alternate boot mode of a memory controller may stream boot image data to a base address of the other memory, and may not be redirected or paused once the streaming of data begins. The other memory, however, may not have sufficient capacity to receive the boot images or may be a memory from which execution of the boot images is not optimal. Thus, some of the boot images may not be streamed or transferred until after the memory controller is fully initialized to enable transfers to other preferred memories. Initializing the memory controller, however, expends computing resources and consumes time, which can slow device boot times.

This disclosure describes apparatuses and techniques for dynamic boot image streaming, which enable boot images to be streamed to non-contiguous memory locations and/or to multiple memories. By so doing, the boot images can be streamed to various memory locations without fully initializing the memory controller, thereby conserving computing resources, saving time, and/or reducing device boot times.

The following discussion describes an operating environment, techniques that may be employed in the operating environment, and a System-on-Chip (SoC) in which components of the operating environment can be embodied. In the discussion below, reference is made to the operating environment by way of example only.

Operating Environment

FIG. 1 illustrates an example of an operating environment 100 having computing devices 102, each of which are capable of communicating, accessing, presenting, or processing various data. Computing devices 102 include smart-phone 104, tablet computer 106, multi-function printer 108, and digital camera 110, and internet-protocol enabled television 112 (IP TV 112). Although not shown, other configurations of computing devices 102 are also contemplated such as a desktop computer, server, mobile-internet device (MID), gaming console, mobile hotspot, networked media player, and so on.

Generally, computing devices 102 have operational states ranging from an “off” state to an “on” state. These states may include a fully off state, suspended state, sleep state, hibernation state, idle state, active state, and the like. When transitioning from a lower operational state to a higher operational state (e.g., from an off state to an active state), computing device 102 is booted. Booting computing device 102 includes transferring and/or executing low-level code to configure components of computing device 102 for operation.

Each computing device 102 includes processor(s) 114 (e.g. an application processor) and computer-readable storage media 116 (CRM 116). Processor 114 includes any suitable number and/or type of processing cores, which may be configured in any suitable manner (e.g., a heterogeneous multi-core application processor). CRM 116 includes volatile memory 118, non-volatile memory 120, and embedded memory 122. Volatile memory 118 includes static random access memory 124 (SRAM 124) and synchronous dynamic random-access memory 126 (DRAM 126). Alternately or additionally, volatile memory 118 may include other suitable types of memory, such as random-access memory (RAM), asynchronous dynamic RAM, double-data-rate RAM (DDR), and the like.

Non-volatile memory 120 includes flash memory 128, which may store data of computing device 102 persistently when powered-down or suspended. Alternately or additionally, non-volatile memory 120 may include other suitable types of memory or storage devices such as non-volatile RAM (NVRAM), read-only memory (ROM), solid-state drives, magnetic or optical disk drives, and the like. Operating systems, applications, or user data (not shown) of computing device 102 may be stored by, or executed from, volatile memory 118, non-volatile memory 120, or any other suitable type of CRM 116. Alternately or additionally, operating systems and/or applications of computing device 102 may be embodied as firmware or other processor-executable instructions, binaries, or code. Operating systems and applications of device 102 are executable by processor 114 to provide a user interface, various functionalities, and/or services of computing device 102.

Embedded memory 122 includes memory controller 130, direct memory access engine 132 (DMA engine 132), and embedded flash memory 134 (embedded flash 134). Embedded memory 122, and components thereof, may be implemented as an integrated memory device, such as an embedded multimedia card (eMMC) device. Memory controller 130 enables access of embedded memory 122 and may provide various data management functions for embedded flash 134, such as error-correction coding, block management, or wear leveling. Memory controller 130 may be implemented as any suitable type of controller, such as a secure digital (SD) host controller. Memory controller 130 supports a variety of data transfer operations, such as an advanced direct memory access (ADMA) transfer algorithm.

The ADMA transfer algorithm is a scatter gather algorithm and operates via a set of transfer and link descriptors. The descriptors may be organized by a descriptor table (not shown), which may be programmed with descriptors describing a series of data transfers between embedded memory 122 and other memories of computing device 102. The descriptors may be executed from the descriptor table without interrupting software executing on processor 114 (e.g., a memory host driver). Memory controller 130 may also support various boot modes, such as an alternate boot mode capable of implementing ADMA transfers. Accordingly, memory controller 130 may be configured to transfer data of embedded flash 134 when computing device 102 is booted.

DMA engine 132 enables direct memory access (DMA) operations between embedded memory 122 and other memories of computing device 102 (e.g., SRAM 124 or DRAM 126). DMA operations transfer data from a source memory to a destination memory without involving a higher-level controller or processor. These DMA operations may include single operation DMA algorithms as defined by the secure digital (SD) host controller standard version 1.00. Additionally, the DMA operations may include scatter gather DMA algorithms (e.g., ADMA) as defined by the SD host controller standard version 2.00. For example, DMA engine 132 may transfer data from embedded flash 134 to SRAM 124 via an ADMA transfer without involving or interrupting memory controller 130 or processor 114. Embedded flash 134 is accessible via memory controller 130 or DMA engine 132, and may contain low-level code (e.g., boot code or boot loaders) useful for booting computing device 102.

Embedded flash 134 may be single-level cell (SLC) or multi-level cell (MLC) based managed flash memory. In some cases, embedded flash may include an area of SLC flash memory and an area of MLC flash memory. Embedded flash 134 may contain boot code or other initialization information useful for booting computing device 102. Contents and partitioning of embedded flash 134 may vary and are described below.

CRM 116 also contains data stream manager 136 (stream manager 136), which in this particular example, is embodied as processor-executable instructions that are executable by processor 114 to implement various functionalities. Alternately or additionally, stream manager 136 may be implemented, in part or whole, via firmware or hardware (not shown) or any suitable combination thereof Stream manager 136 may enable boot images or boot data stored by embedded flash 134 to be streamed to non-contiguous memory locations and/or to multiple destination memory devices. The implementation and use of stream manager 136 varies and is described below.

Computing device 102 may also include I/O ports 138, display 140, and network interface(s) 142. I/0 ports 138 allow computing device 102 to interact with other devices or users. I/O ports 138 may include any combination of internal or external ports, such as USB ports, audio ports, Serial ATA (SATA) ports, PCI-express based ports or card-slots, secure digital input/output (SDIO) slots, and/or other legacy ports. Various peripherals may be operatively coupled with I/O ports 138, such as human-input devices (HIDs), external computer-readable storage media, or other peripherals.

Display 140 may present a user interface or rendered graphics associated with an operating system or application of computing device 102. Display 140 may include a touch-input sensor (not shown), such as a touch screen or touch-sensitive overlay. Network interface(s) 142 provides connectivity to one or more networks and other devices connected therewith. Data communicated over network interfaces 142 may be packetized or framed depending on a communication protocol or standard by which computing device 102 is communicating. Network interfaces 142 may include wired interfaces, such as Ethernet or fiber optic interfaces for communication over a local network, intranet, or the Internet. Network interfaces 142 may also include wireless interfaces that facilitate communication over wireless networks, such as wireless LANs, cellular networks, or wireless personal-area-networks (WPANs).

FIG. 2 illustrates an example of embedded flash 134 generally at 200. Embedded flash 134 includes boot partition 202 and data partition 204, capacities of which may be configured to any suitable size or number of data blocks. Data partition 204 may include data associated with an operating system, applications, hardware drivers, user data, and the like. Boot partition includes boot code (e.g., low-level code) and other data useful for configuring components of, and subsequently booting, computing device 102. In this particular example, boot partition 202 includes boot image-0 206, boot image-1 208, and boot image-2 210 (referred to collectively as boot images 206-210). Boot partition 202 may also include boot code or data useful for constructing descriptors for streaming boot images 206-210 from boot partition 202. Boot images 206-210 may include any suitable code, such as boot code, boot loaders, initialization data, headers, address tables, descriptors, firmware, configuration instructions, and the like.

Boot image-0 206 includes header 212 and is streamed from boot partition 202 using a transfer descriptor. Header 212 includes descriptor data 214, which is useful to construct transfer descriptors for streaming boot image-1 208 and/or boot image-2 210 from boot partition 202. Header 212 may also include data useful for configuring other memories of computing device 102, such as DRAM 126. Header 212 may include any suitable amount of data, such as 16 or 32 blocks of data.

Transfer descriptors typically include a destination address, a length indicator specifying an amount of data to transfer, and various attribute fields (e.g., descriptor type, validity, end, interrupt action). In this particular example, a transfer descriptor for transferring boot image-0 206 includes information or parameters for streaming header 212 from embedded flash 134. This descriptor and a link-to-self descriptor may be constructed in volatile memory (e.g., SRAM 124) prior to being input into DMA engine 132 for execution. The link-to-self descriptor is a link type descriptor that references, or points back to, itself Causing a memory controller to execute the link-to-self descriptor may be effective to stall the memory controller. Alternately or additionally, executing a link-to-self descriptor may stall data lines or a clock line of a memory controller. The use of the link-to-self descriptor may vary and is described below.

Techniques of Dynamic Boot Image Streaming

The following discussion describes techniques of dynamic boot image streaming. These techniques can be implemented using the previously described environment or entities, such as memory controller 130 or stream manager 136 of FIG. 1 embodied on a computing device 102. These techniques include methods illustrated in FIGS. 3, 5, and 6, each of which is shown as a set of operations performed by one or more entities. These methods are not necessarily limited to the orders shown for performing the operations. Further, these methods may be used in conjunction with one another, in whole or in part, whether performed by the same entity, separate entities, or any combination thereof In portions of the following discussion, reference will be made to operating environment 100 of FIG. 1 and entities of FIGS. 2 and 4 by way of example. Such reference is not to be taken as limited to operating environment 100 but rather as illustrative of one of a variety of examples.

FIG. 3 depicts a method 300 for stalling a memory controller streaming multiple boot images, including operations performed by stream manager 136 of FIG. 1.

At 302, a streaming of multiple boot images from a first memory to a second memory is initiated. The streaming may be initiated responsive to a power-on event or a command (e.g., a boot initiation command). The multiple boot images are streamed by a memory controller or DMA engine associated with the first memory. The streaming operations performed by the memory controller or DMA engine are based on one or more ADMA transfer and/or link descriptors. A first one of the boot images may include transfer descriptors and/or a header of fixed length, such as 16 or 32 data blocks. This header includes information useful to construct additional descriptors or to configure other memories. Other ones of the multiple boot images may include boot loaders, configuration files, operating systems, boot code, and the like.

As an example, consider a user powering-on smart-phone 104 of FIG. 1. Assume here that smart-phone 104 is transitioning to an “on” state from an “off” state in which power was removed from volatile memory 118 and other various components of smart-phone 104. Here, stream manager 136 sends a boot initiation command (e.g., CMD_0 0xFFFFFFFA) to memory controller 130 of embedded memory 122, which may be configured as an eMMC device. Stream manager 136 then points EXT_CSD register of memory controller 130 to a transfer descriptor when initiating a streaming operation. In some cases, stream manager 136 may construct the transfer descriptor and/or a link-to-self descriptor prior to initiating the streaming operation. The transfer descriptor indicates a destination address of SRAM 124 to which boot image-0 206 (header 212) is to be streamed. DMA engine 132, which is associated with memory controller 130, then begins to stream boot image-0 206 to SRAM 124 as illustrated in FIG. 4.

At 304, a memory controller that is streaming the multiple boot images is stalled. The memory controller may be stalled after a first one of the boot images is streamed into the second memory. The first one of the boot images may be a header file including data useful to construct transfer descriptors for other ones of the multiple boot images. The memory controller may be stalled by causing the memory controller to execute a link-to-self descriptor. In some cases, the memory controller is configured to incrementally execute a series of descriptors during the streaming operation. In such case, the link-to-self descriptor may be placed in a memory location following a location of the descriptor for streaming the first boot image.

In the context of the present example, assume that a link-to-self descriptor is located at an address following the transfer descriptor. Once memory controller 130 of embedded memory 122 executes the transfer descriptor to stream boot image-0 206 via DMA engine 132, a system address register of memory controller 130 is incremented to the address of the link-to-self descriptor. Memory controller 130 then begins executing the link-to-self descriptor, and operation of memory controller 130 stalls. Executing the link-to-self descriptor also stalls a clock line of embedded memory 122 and DMA engine 132.

At 306, a descriptor for streaming a second one of the multiple boot images is generated while the memory controller is stalled. This descriptor is generated by a processor executing code of the first boot image (e.g., descriptor data 214 of header 212) from the second memory. The descriptor is a transfer descriptor for streaming the second boot image to a non-contiguous location of the second memory or a third memory. In some cases, the descriptor is constructed from a header previously streamed to the second memory. Alternately or additionally, the header may include initialization data for the third memory, such as data for configuring for DRAM or DDR. Memory controller 130 and DMA engine 132 are not necessarily aware of being stalled while the descriptor is generated.

Continuing the ongoing example, stream manager 136 causes processor 114 to execute boot code of header 212 from SRAM 124 to construct additional descriptors. These additional descriptors are associated with boot image-1 208 and boot image-2 210. Processor 114 also executes the boot code of header 212 to configure DRAM 126 for receiving boot image-1 208 and boot image-2 210. In other instances, the additional descriptors are configured to stream boot images to non-contiguous locations of SRAM 124, such as specifying offsets between destination addresses for the boot images.

At 308, the memory controller is resumed to stream the second boot image to the non-contiguous location of the second memory or to the third memory. The memory controller is resumed by pointing the link-to-self descriptor to a descriptor for streaming the second boot image. Resuming the memory controller causes the DMA engine to continue the streaming operation initiated at 302 without interrupting a host controller driver. Resuming the memory controller also resumes data lines or the clock line associated with the memory controller. By so doing, boot images can be streamed to non-contiguous and/or non-sequential locations of multiple memories with a single streaming operation (e.g. ADMA transfers in alternate boot mode).

Concluding the present example, stream manager 136 points the link-to-self descriptor being executing by memory controller 130 to a first of the additional descriptors generated while memory controller 130 was stalled. This is effective to cause memory controller 130 to resume the streaming operation boot image-1 208 and boot image-2 210 based on the additional link descriptors. Here, DMA engine 132 streams boot image-1 208 and boot image-2 210 to non-contiguous and non-sequential locations of DRAM 126 as illustrated by FIG. 4. Processor 114 can then complete the boot process of smart-phone 104 by executing the boot code from the respective locations of SRAM 124 and DRAM 126.

FIG. 5 depicts a method 500 for streaming boot images to non-contiguous locations of a memory device, including operations performed by stream manager 136 of FIG. 1.

At 502, a boot initialization command is sent to a first memory device. In some cases, the memory device may be an embedded memory device configured to transfer boot code, such as an eMMC memory device. The boot initialization command is sent to a controller of the first memory device. Alternately or additionally, a pre-idle command may be sent to the memory controller to put the memory device into an initial power-on-reset mode. The pre-idle command may be sent prior to sending the boot initialization command to the memory device. The memory device is pre-configured to stream a boot image responsive to the boot initialization command. For example, a boot partition and associated size of the boot partition are set in a register accessible by the memory controller (e.g., an EXT_CSD register). In some cases, the boot initialization command is sufficient to cause the memory device to start memory transfers associated with booting a device.

At 504, a controller of the first memory device is caused to execute a descriptor for streaming a header to a second memory device. An address of the descriptor may be indicated by a register of the controller. The descriptor indicates a length of the header, such as 16 or 32 data blocks. In some cases, the header is streamed by a DMA engine associated with the controller. The second memory device may be a memory device that needs little or no pre-configuration prior to receiving the header, such as SRAM and the like.

At 506, the controller of the first memory device is caused to execute a link-to-self descriptor effective to stall the controller of the memory device. In some cases, stalling the controller stalls data lines or a clock line associated with the controller. Alternately or additionally, a DMA engine associated with the controller may also be stalled while the controller executes the link-to-self descriptor. For example, stream manager 136 may cause memory controller 130 to execute a link-to-self descriptor after a header is streamed into SRAM.

At 508, the header is processed to construct additional descriptors for streaming one or more boot images to non-contiguous locations of the second memory device. The header is executed from the second memory device by a processor to construct the additional descriptors. The additional descriptors may be constructed while the memory controller is stalled. In some cases, the one or more boot images include boot loader or boot code for configuring components of a device for use. The second memory can be a volatile memory from which the one or more boot images are executed from.

At 510, the link-to-self descriptor is pointed to the additional descriptors effective to resume the controller of the first memory device. The first memory device then streams the one or more boot images to non-contiguous locations of the second memory device. For example, stream manager 136 may point a link-to-self descriptor being executed by memory controller 130 to data descriptors for streaming boot images 206-210 or remaining code thereof

FIG. 6 depicts a method 600 for streaming boot images to multiple memory devices, including operations performed by stream manager 136 of FIG. 1.

At 602, a boot initialization command is sent to a first memory device. In some cases, the first memory device is an embedded memory device configured to transfer boot code during a boot sequence, such as an eMMC memory device. A pre-idle command (e.g., CMD 0xF0F0F0F0) can be sent prior to the boot initialization command to put the first memory device in a pre-idle state. The boot initialization command is sent to a controller of the first memory device. In some cases, the first memory device is pre-configured to stream a boot image responsive to the boot initialization command. For example, a boot partition and associated size of the boot partition may be set in a register accessible by the memory controller (e.g., an EXT_CSD register). In such cases, the boot initialization command is sufficient to cause a controller to start streaming boot images from the first memory device.

At 604, a controller of the first memory device is caused to execute a descriptor for streaming a header to a second memory device. An address of the descriptor is indicated by a register of the controller. The descriptor may also indicate a length of the header, such as 16 or 32 data blocks. In some cases, the header is streamed by a DMA engine associated with the controller. The second memory device may be a memory device that needs little or no pre-configuration prior to receiving the header, such as SRAM and the like.

At 606, the controller of the first memory device is caused to execute a link-to-self descriptor effective to stall the controller of the memory device. Stalling the controller may stall data lines or a clock line associated with the controller. Alternately or additionally, a DMA engine associated with the controller may also be stalled while the controller executes the link-to-self descriptor. For example, stream manager 136 can cause memory controller 130 to execute a link-to-self descriptor after a header is streamed into SRAM.

At 608, the header is processed to construct additional descriptors for streaming multiple boot images to a third memory device. The header may be executed from the second memory device by a processor to construct the additional descriptors. The additional descriptors are constructed while the memory controller is stalled. In some cases, the multiple boot images include boot loader or boot code for configuring components of a device for use. The third memory device is a volatile memory that is of a different type than that of the second memory device. For example, the second memory device may comprise SRAM and the third memory device may comprise DRAM.

At 610, the third memory device is configured to receive a boot image streamed from the first memory device. In some cases, third memory is configured based on data or information included in the header. In such cases, the processor executes additional data of the header to configure the third memory device. Configuring the third memory device may include setting various parameters associated with the third memory device, such as bus settings, data rate settings, bank address settings, and the like.

At 612, the link-to-self descriptor is pointed to the additional descriptors effective to resume the controller of the first memory device. The first memory device then streams the multiple boot images to the third memory device. For example, stream manager 136 may point a link-to-self descriptor being executed by memory controller 130 to data descriptors for streaming boot images 206-210. The multiple boot images are streamed to non-contiguous and/or non-sequential locations of the third memory device. For example, boot image-2 210 can be streamed to a base address of DRAM 126 and boot image-1 208 may be streamed to another non-contiguous location of DRAM 126 as illustrated in FIG. 4.

System-on-Chip

FIG. 7 illustrates a System-on-Chip (SoC) 700, which can implement various aspects of dynamic boot image streaming. A SoC can be implemented in any suitable device, such as a video game console, IP-enabled television, smart-phone, desktop computer, laptop computer, access point, wireless router, cellular broadband router, tablet computer, server, network-enabled printer, set-top box, printer, scanner, camera, picture frame, home appliance, thermostat, home automation device, and/or any other type of electronic device.

SoC 700 can be integrated with electronic circuitry, a microprocessor, memory, input-output (I/O) logic control, communication interfaces, other hardware, firmware, and/or software needed to provide functionalities of a device, such as any of the above-listed devices. SoC 700 can also include an integrated data bus (not shown) that couples the various components of the SoC for data communication between the components. A memory storage device that includes SoC 700 can also be implemented with many combinations of differing components. In some cases, these differing components may be configured to implement concepts described herein over various internal or external data interfaces.

In this example, SoC 700 includes various components such as an input-output (I/O) logic control 702 (e.g., to include electronic circuitry) and microprocessor 704. SoC 700 also includes memory 706, which can be any type and/or combination of RAM, SRAM, DRAM, low-latency nonvolatile memory, ROM, one-time programmable (OTP) memory, and/or other suitable electronic data storage. Alternately or additionally, SoC 700 may comprise a data interface (not shown) for accessing additional or expandable off-chip memory, such as external SRAM, DRAM, or flash memory. SoC 700 can also include various firmware and/or software, such as operating system(s) 708, which can be computer-executable instructions maintained by memory 706 and executed by microprocessor 704. SoC 700 may also include other various communication interfaces and components embodied as hardware, firmware, software, or any suitable combination thereof.

SoC 700 also includes memory controller 130, DMA engine 132 embedded flash 134, and stream manager 136 (either of which may embodied as disparate or combined components). Although not shown, embedded flash 134 may include boot partition 202 and data partition 204, for storing any suitable data (e.g., user data or boot images 206-210). Examples of these various components, functions, and/or entities, and their corresponding functionality, are described with reference to the respective components of the environment 100 and various configurations as illustrated by FIGS. 2 and 4.

Stream manager 136, either independently or in combination with other entities (e.g., memory controller 130), can be implemented as computer-executable instructions maintained by memory 706 and executed by microprocessor 704 to implement various embodiments and/or features described herein. Stream manager 136 may also be provided integral with other entities of the SoC, such as integrated a memory controller associated with memory 706 or another suitable software, firmware, or hardware component within SoC 700. Alternatively or additionally, stream manager 136 and the other components can be implemented as hardware, firmware, fixed logic circuitry, or any combination thereof that is implemented in connection with the I/O logic control 702 and/or other signal processing and control circuits of SoC 700.

Although the subject matter has been described in language specific to structural features and/or methodological operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or operations described above, including orders in which they are performed. 

What is claimed is:
 1. A method comprising: stalling a memory controller that is streaming, via a direct memory access (DMA) operation, multiple boot images from a first memory to a second memory, the stalling performed after streaming a first one of the multiple boot images to the second memory; generating, while the memory controller is stalled and based on the first boot image streamed to the second memory, a descriptor for streaming a second one of the multiple boot images from the first memory to a non-contiguous memory location; and resuming the memory controller effective to cause the memory controller to stream, based on the descriptor and via another DMA operation, the second boot image to the non-contiguous memory location.
 2. The method of claim 1, wherein stalling the memory controller includes causing the memory controller to execute a link-to-self descriptor.
 3. The method of claim 2, wherein resuming the memory controller includes pointing the link-to-self descriptor executed by the memory controller to a location of the descriptor generated while the memory controller is stalled.
 4. The method of claim 2, wherein the first boot image streamed to the second memory includes the link-to-self descriptor and information useful to generate the descriptor for streaming the second boot image.
 5. The method of claim 1, wherein stalling the memory controller stalls a clock line of the memory controller.
 6. The method of claim 1, wherein the DMA operation and the other DMA operation are performed via a DMA engine associated with the memory controller.
 7. The method of claim 1, wherein the memory controller and the first memory are embodied as part of an embedded multimedia card (eMMC) device.
 8. The method of claim 1, wherein: the first memory is single-level cell (SLC) or multi-level cell (MLC) NAND based managed flash memory; and the second memory is static random-access memory (SRAM).
 9. The method of claim 1, wherein the non-contiguous memory location is a memory location of the second memory or a third memory.
 10. The method of claim 9, wherein the third memory is dynamic random-access memory (DRAM), and further comprising configuring, while the memory controller is stalled, the third memory to receive the second boot image from the first memory.
 11. A memory storage device comprising: a controller configured to provide an interface to a data bus of a host device; a direct memory access (DMA) engine configured to stream data of the memory storage device to another memory storage device of the host device via the data bus; and memory storage media configured to store the data of the memory storage device, the data of the memory storage device including: multiple boot images executable from the other memory storage device by a processor of the host device to initialize components of the host device during a boot sequence; a header executable by the processor of the host device to construct a series of data transfer commands for streaming the multiple boot images, via the DMA engine, to non-contiguous locations of the other memory storage device; another data transfer command associated with the header that, when executed by the controller, streams the header, via the DMA engine, to a base address of the other memory storage device; and a data link command that, when executed by the controller, stalls the DMA engine effective to permit the header to be executed from the other memory storage device by the processor to construct the series of data transfer commands for streaming, via the DMA engine, the multiple boot images.
 12. The memory storage device of claim 11, wherein the series of data transfer commands and the other data transfer command are advanced direct memory access (ADMA) transfer descriptors and the data link command is an ADMA link descriptor.
 13. The memory storage device of claim 12, wherein the ADMA link descriptor is a link-to-self descriptor that, when executed by the controller, stalls the controller until the link-to-self descriptor is pointed to an address of one of the ADMA transfer descriptors.
 14. The memory storage device of claim 11, wherein stalling the controller stalls a clock line or data lines associated with the controller.
 15. The memory storage device of claim 11, wherein the memory storage device is embodied as an embedded multimedia card (eMMC) device, the controller is a secure digital (SD) host controller, and the memory storage media is flash memory.
 16. The memory storage device of claim 15, wherein the eMMC device is compliant with version 4.3 of the Joint Electron Device Engineering Council (JECEC) multimedia card (MMC) standard.
 17. One or more computer-readable storage devices embodying processor-executable instructions that, when executed by a processor, implement a stream manager to: stall a memory controller that is streaming, via a direct memory access (DMA) operation, multiple boot images from a non-volatile memory to a volatile memory from which the multiple boot images are executable by the processor, the memory controller stalled after streaming a first one of the multiple boot images to the volatile memory; generate, while the memory controller is stalled and based on the first boot image streamed to the volatile memory, a descriptor for streaming a second one of the multiple boot images from the non-volatile memory to a non-contiguous location of the volatile memory; and resume the memory controller effective to cause the memory controller to stream, based on the descriptor and via another DMA operation, the second boot image to the non-contiguous location of the volatile memory.
 18. The one or more computer-readable storage devices of claim 17, wherein the stream manager stalls the memory controller by causing the memory controller to execute a link-to-self descriptor and resumes the memory controller by pointing the link-to-self descriptor executed by the memory controller to a location of the descriptor generated while the memory controller is stalled.
 19. The one or more computer-readable storage devices of claim 17, wherein the memory controller and non-volatile memory are embodied as an embedded multimedia card (eMMC) device.
 20. The one or more computer-readable storage devices of claim 17, wherein the stream manager is further configured to initiate the streaming of the multiple boot images responsive to a single command or power event. 